Could there be an æther after all and we have just not yet noticed it? By an “æther” of course we do not mean to suggest a mechanical medium whose deformations correspond to electromagnetic fields, but rather a locally preferred state of rest at each point of spacetime, determined by some hitherto unknown physics. Such a frame would not be determined by a circumstance such as the moon’s gravita...

The scale at which supersymmetry is broken and the mechanism by which supersymmetry breaking is fed down to the observable sector has rich implications on the way Nature may have chosen to accomplish inflation. We discuss a simple model for slow rollover inflation which is minimal in the sense that the inflaton may be identified with the field responsible for the generation of the μ-term. Infla...

Whether we live in a spatially finite universe, and what its shape and size may be, are among the fundamental long-standing questions in cosmology. These questions of topological nature have become particularly topical, given the wealth of increasingly accurate astro-cosmological observations, especially the recent observations of the cosmic microwave background radiation. An overview of the ba...

A short introduction to structure formation is given, followed by a discussion of the possible characteristics of the initial perturbations assuming a generic inflationary origin. Observational data related to large-scale structure and the cosmic microwave background radiation is then used in an attempt to constrain the characteristics of such perturbations. Future directions are also explored....

What is the shape of the Universe? Is it curved or flat, finite or infinite ? Is space “wrapped around” to create ghost images of faraway cosmic sources? We review how tessellations allow to build multiply-connected 3D Riemannian spaces useful for cosmology. We discuss more particularly the proposal of a finite, positively curved, dodecahedral space for explaining some puzzling features of the ...

As a part of the ISOPHOT CIRB (Cosmic Infrared Background Radiation) project we have searched for point-like sources in eight fields mapped at two or three wavelengths between 90μm and 180μm. Most of the 55 sources detected are suspected to be extragalactic and cannot be associated with previously known objects. It is probable, also from the far-infrared (FIR) spectral energy distributions, tha...

Assuming that the cosmological principle holds, Maartens, Ellis and Stoeger (MES) recently constructed a detailed scheme linking anisotropies in the cosmic background radiation (CMB) with anisotropies and inhomogeneities in the large scale structure of the universe and showed how to place limits on those anisotropies and inhomogeneities simply by using CMB quadrupole and octupole limits. First ...

Banks and Dine have recently shown that the M theory naturally accommodates the Peccei-Quinn axion. Since the decay constant F a of the axion is large as F a ≃ 10 15 − 10 16 GeV, the halo axion is hardly detected in coming axion-search experiments. However, we show that isocurvature fluctuations of the M-theory axion produced at the inflationary epoch are most likely detectable in future satell...

The possibility to constrain fractal space dimensionality from Astrophysics and other areas is briefly reviewed. Using data from FIRAS instrument aboard COBE satellite and assuming space dimensionality to be 3 + ǫ, we calculate ǫ = −(0.957 ± 0.006) × 10 and an absolute temperature 2.726 ± 0.003 × 10 K by fitting the cosmic microwave background radiation spectrum to Planck’s radiation distributi...

The RXTE satellite observed the Coma cluster for ∼177 ks during November and December 2000, a second observation motivated by the intriguing results from the first ∼87 ks observation in 1996. Analysis of the new dataset confirms that thermal emission from isothermal gas does not provide a good fit to the spectral distribution of the emission from the inner 1 radial region. While the observed sp...